The present disclosure relates to a multiple parameter sensor-transmitter/receiver unit which may be installed on or removed from an energized electric power line, such as an overhead power line. With the advent of Smart-Grid applications for electric power systems, there is an ever increasing need for a device that measures electric, mechanical, and environmental parameters of the power line.
In order to address the increasing need for monitoring power lines, devices have been developed that attach directly to the power line. These devices generally require a power source, such as batteries or solar panels. When utilizing batteries, regular maintenance must be performed to replace the batteries, which can become costly. When solar panels are used, the device may only be powered during sunny weather conditions and during daylight hours. Therefore, there is a need for a device which is low maintenance and can be constantly powered independent of weather conditions.
Electric power line conductors are usually stranded conductors including a number of strands of wire wrapped into a concentrically wound complete cylindrical conductor. This is done to introduce flexibility into large diameter conductors. Large diameter solid conductors are not used because they are too rigid for line conductors. When a device for measuring the conductor temperature of a stranded conductor carrying current is physically placed onto the conductor the surface conductor temperature will be lowered at the location of said device on the conductor, because the temperature of this device is lower than the conductor temperature of the line and the heat generated within the conductor due to the I2R (current squared times conductor resistance) losses will be conducted away from the conductor and onto the device where the heat is then thermally radiated and convected away into the lower temperature ambient or environment.
The most important parameter in determining the real time current carrying capacity of an overhead electric power line is the conductor temperature. This is one of the parameters used to determine (1) the thermal state of the overhead line conductor, (2) the line sag including elevated temperature creep (which causes the line to permanently increase in length due to high conductor temperature operation), (3) the loss of conductor tensile strength, and (4) the temperature effect on line hardware such as conductor dead ends connected to the line supporting structures and the line splices connecting the conductors together. Having an accurate method of measuring the conductor temperature insures the line does not sag down beyond the minimum clearance of the power line to the earth or to an object under the line, because as the line heats up due to the current flowing in the line, the conductor elongates due to thermal expansion. Also, the maximum allowable current, or the thermal rating of the line, is limited by the maximum conductor temperature so that both the line clearance is not exceeded due to increased sag and the loss of conductor tensile strength criteria is not exceeded. Therefore, there is a need for a device which is low maintenance and can be provide an undisturbed conductor temperature reading.